Resolving the Formation Mechanism of HONO via Ammonia-Promoted Photosensitized Conversion of Monomeric NO on Urban Glass Surfaces.

Understanding the formation processes of nitrous acid (HONO) is crucial due to its role as a primary source of hydroxyl radicals (OH) in the urban atmosphere and its involvement in haze events. In this study, we propose a new pathway for HONO formation via the UVA-light-promoted photosensitized conversion of nitrogen dioxide (NO) in the presence of ammonia (NH) and polycyclic aromatic hydrocarbons (PAHs, common compounds in urban grime). This new mechanism differs from the traditional mechanism, as it does not require the formation of the NO dimer.

Heterogeneous chemistry of ozone with floor cleaning agent: Implications of secondary VOCs in the indoor environment.

Human daily activities such as cooking, and cleaning can affect the indoor air quality by releasing primary emitted volatile organic compounds (VOCs), as well as by the secondary product compounds formed through reactions with ozone (O) and hydroxyl radicals (OH). However, our knowledge about the formation processes of the secondary VOCs is still incomplete. We performed real-time measurements of primary VOCs released by commercial floor-cleaning detergent and the secondary product compounds formed by heterogeneous reaction of O with the constituents of the cleaning agent by use of high-resolution mass spectrometry.

The Effect of Human Occupancy on Indoor Air Quality through Real-Time Measurements of Key Pollutants.

The primarily emitted compounds by human presence, e.g., skin and volatile organic compounds (VOCs) in breath, can react with typical indoor air oxidants, ozone (O), and hydroxyl radicals (OH), leading to secondary organic compounds.

Daytime SO chemistry on ubiquitous urban surfaces as a source of organic sulfur compounds in ambient air.

The reactions of sulfur dioxide (SO) with surface-bound compounds on atmospheric aerosols lead to the formation of organic sulfur (OS) compounds, thereby affecting the air quality and climate. Here, we show that the heterogeneous reaction of SO with authentic urban grime under near-ultraviolet sunlight irradiation leads to a large suite of various organic compounds including OS released in the gas phase. Calculations indicate that at the core area of Guangzhou, building surface uptake of SO is 15 times larger than uptake of SO on aerosol surfaces, yielding ~20 ng m of OS that represents an important fraction of the observed OS compounds (60 to 200 ng m) in ambient aerosols of Chinese megacities.

Unveiling the pH-Dependent Yields of HO and OH by Aqueous-Phase Ozonolysis of -Cresol in the Atmosphere.

Hydrogen peroxide (HO) and hydroxyl radical (OH) are important oxidants in the atmospheric aqueous phase such as cloud droplets and deliquescent aerosol particles, playing a significant role in the chemical transformation of organic and inorganic pollutants in the atmosphere. Atmospheric aqueous-phase chemistry has been considered to be a source of HO and OH. However, our understanding of the mechanisms of their formation in atmospheric waters is still incomplete.

Physical and chemical characterization of urban grime: An impact on the NO uptake coefficients and N-containing product compounds.

Urban grime represents an important environmental surface for heterogeneous reactions in urban environment. Here, we assess the physical and chemical properties of urban grime collected during six consecutive months in downtown of Guangzhou, China. There is a significant variation of the uptake coefficients of NO on the urban grime as a function of the relative humidity (RH).

Inorganic Ions Enhance the Number of Product Compounds through Heterogeneous Processing of Gaseous NO on an Aqueous Layer of Acetosyringone.

Methoxyphenols represent important pollutants that can participate in the formation of secondary organic aerosols (SOAs) through chemical reactions with atmospheric oxidants. In this study, we determine the influence of ionic strength, pH, and temperature on the heterogeneous reaction of NO with an aqueous film consisting of acetosyringone (ACS), as a proxy for methoxyphenols. The uptake coefficient of NO (50 ppb) on ACS (1 × 10 mol L) is γ = (9.

Effect of Inorganic Salts on N-Containing Organic Compounds Formed by Heterogeneous Reaction of NO with Oleic Acid.

Fatty acids are ubiquitous constituents of grime on urban and indoor surfaces and they represent important surfactants on organic aerosol particles in the atmosphere. Here, we assess the heterogeneous processing of NO on films consisting of pure oleic acid (OA) or a mixture of OA and representative salts for urban grime and aerosol particles, namely NaSO and NaNO. The uptake coefficients of NO on OA under light irradiation (300 nm < λ < 400 nm) decreased with increasing relative humidity (RH), from (1.

Ionic Strength Effect Triggers Brown Carbon Formation through Heterogeneous Ozone Processing of Ortho-Vanillin.

Methoxyphenols are an important class of compounds emerging from biomass combustion, and their reactions with ozone can generate secondary organic aerosols in the atmosphere. Here, we use a vertical wetted wall flow tube reactor to evaluate the effect of ionic strength on the heterogeneous reaction of gas-phase ozone (O) with a liquid film of -vanillin (-VL) (2-hydroxy-3-methoxybenzaldehyde), as a proxy for methoxyphenols. Typical for moderately acidic aerosols, at fixed pH = 5.

Unexpectedly High Indoor HONO Concentrations Associated with Photochemical NO Transformation on Glass Windows.

Nitrous acid (HONO) is an important gaseous pollutant contributing to indoor air pollution because it causes adverse health effects and is the main source of hydroxyl radicals (OH). Here, we present direct measurements of HONO produced through light-induced heterogeneous reactions of NO with grime adsorbed on glass window. The uptake coefficients of NO [γ(NO)] on the glass plates from the kitchen increased markedly from (2.

Light-Enhanced Heterogeneous Conversion of NO to HONO on Solid Films Consisting of Fluorene and Fluorene/NaSO: An Impact on Urban and Indoor Atmosphere.

Polycyclic aromatic hydrocarbons (PAHs) as constituents of urban grime and indoor surfaces can impact the photochemical conversion of nitrogen dioxide (NO) to nitrous acid (HONO) thereby impacting the oxidation capacity of the atmosphere. In this study we investigate the effect of relative humidity (RH%), light intensity, and NO concentrations on uptake coefficients (γ) of NO on solid film consisting of fluorene (FL) and a mixture of FL and NaSO as a proxy for urban and indoor grime at ambient pressure and temperature. γ(NO) on solid FL increased markedly from (5.